As reported in Breakthroughs last year, their paper proposes a design for a successor to the Kyoto Protocol.
"The successor to the Kyoto Protocol should impose national ceilings on rich countries' greenhouse gas emissions and promote voluntary abatement by developing countries," the authors write. "Our proposal gives signatories the option of exercising an escape clause that relaxes their requirement to abate. This feature helps to solve the participation and compliance problems that have weakened the Protocol. We support the use of carefully circumscribed trade restrictions in order to reduce the real or perceived problem of carbon leakage."
The full paper is available here.